jf8b04566_si_001.pdf (366.55 kB)
Molecular Engineering of Bacillus paralicheniformis Acid Urease To Degrade Urea and Ethyl Carbamate in Model Chinese Rice Wine
journal contribution
posted on 2018-11-19, 00:00 authored by Qingtao Liu, Xinhui Yao, Qixing Liang, Jianghua Li, Fang Fang, Guocheng Du, Zhen KangBacillus paralicheniformis urease
(BpUrease) has been shown to be a promising biocatalyst for degrading
the carcinogenic chemical ethyl carbamate (EC or urethane) in rice
wine. However, low EC affinity and catalytic efficiency limit the
practical application of BpUrease. In this study, we improved the
EC degradation capability of BpUrease by site-saturation mutagenesis
(SSM). The best variant L253P/L287N showed a 49% increase in EC affinity,
1027% increase in catalytic efficiency (kcat/Km), and 583% increase in half-life
(t1/2) at 70 °C. Homology modeling
analysis suggest that mutation of Leu253 to Pro increased the BpUrease
EC specificity by affecting the interaction between Arg339 with the
catalytic residue His323, while Leu287Asn mutation benefits EC specificity
and affinity by changing the interaction networks among the residues
in the catalytic pocket. Our results show that the L253P/L287N variant
efficiently degraded urea and EC in a model rice wine, making it a
good candidate for practical application in the food industry.